DE102008018387B4 - Method and device for movement correction - Google Patents

Abstract

The invention relates to a method and a device for movement correction during imaging during a medical intervention of a patient. Prior to the intervention, a preferably tomographic 3-D image (11) of a target area of the intervention is recorded, during the intervention a 2-D image (13) of the target area is recorded and registered with the 3-D image (11), In the 2-D image (13), visible image features (24, 26) of moving structures (14, 24, 26) are automatically determined or identified, in further 2-D images (13) taken from the same projection. the movement (28) of the patient is determined from these visible image features (24, 26). Furthermore, existing image features in the 2-D image (13) are determined or identified as so-called anatomical fixed points (30) by structures which are virtually rigid and / or independent of the movement, wherein a correction of the 2-D / 3-D registration to compensate for the previously determined movement (28) is calculated and the 2-D images (13) are visualized together with the 3-D image (11, 25) and the 3-D Images (11, 25) and / or 2-D images (13) of the movement (28) are adjusted accordingly.

Description

The The invention relates to a method and a device for movement correction in intra-operative imaging during a medical, for example, abdominal intervention

During one Intervention will be used to navigate the instruments, for example in the abdomen, using fluoroscopic fluoroscopy real-time images won. Compared to 3-D angio images, these fluoroscopy or 2-D images though no spatial (3-D) details, but they are faster available and minimize radiation exposure for patient and doctor. Ideally, the spatial information is now recovered that pre- or Intraoperatively recorded 3-D images z. From CT, 3-D angio, C-arm CT or MR images be registered with the two-dimensional images and this be underlaid. The combination of co-registered 2-D and 3-D images now allow the doctor a better orientation in the volume. This 2-D / 3-D registration consists of two steps.

1st picture registration:

First of all must determine from which direction a 3-D volume must be projected so that it can be brought into line with the 2-D image. There are for this different approaches, which are described for example in Penney [1].

2. Visualization:

The second problem is the visualization of the registered images, ie the joint representation of 2-D image and projected 3-D image. The standard method for this is the so-called "overlay", in which the two images are superimposed by different methods, as for example in the earlier patent application DE 10 2006 003 126 A1 is described.

One Problem of 2-D / 3-D registration, especially in abdominal applications, such as in liver punctures or in navigation in the Vascular System liver, is that the 3-D images are static, d. H. taken in a certain respiratory phase. In the 2-D pictures However, the respiratory movements are clearly visible.

The Registration of 3-D images to 2-D X-ray images is from "Registration of Tomographic Images to X-ray Projections for Use in Image Guided Intervention "of Graeme Patrick Penney [1] known.

For other applications, such as CT-guided interventions or MR examinations, the respiratory movement is often determined by external sensors, for example in belts placed around the diaphragm, as described, for example, in US Pat US 5,088,501 A is described.

In the earlier patent application DE 10 2005 059 804 A1 It has been proposed to first record a tomographic 3-D image of a target area of the intervention while one or more medical instruments are in the target area remaining in the target area during the intervention. During the intervention, fluoroscopic 2-D fluoroscopic images of the target area are recorded and registered with the 3-D image. The registration is performed in each case on the basis of one or more instruments for each 2-D fluoroscopic image in real time. The 2-D fluoroscopic images are then visualized in each case with image representations of the 3-D image which correspond in perspective.

In the earlier patent application DE 10 2007 015 792.6 has already been proposed a correction method for movement correction. In the already proposed method, the breathing direction is determined and the 3-D overlay is shifted accordingly. This approach has the disadvantage that when interventions are made in areas that are very inhomogeneous with respiration (eg parts of the abdomen or heart), the already proposed correction is insufficient.

In the published patent application DE 10 2006 024 000 A1 is a method and apparatus for visualizing objects describe. In particular, the visualization of non-rigid objects is described here. A series of two-dimensional or three-dimensional image data sets is created, which follow each other in time. Each individual image data set of the series is registered individually, eg. B. to the temporally preceding image data set or to a pre-created three-dimensional image data set of the object. This individual registration is very complex and can only be used with slight respiratory or heart movements.

The Invention is based on the object, a method of the aforementioned Form such a way that in a simple way an adaptation of static 3-D images and dynamic 2-D images. The registration must therefore in particular in inhomogeneous z. B. shifted by breathing movements Be adapted to areas.

This object is achieved by the method and device-related features specified in the independent patent claims. Advantageous developments of the invention are specified in the dependent claims.

• – Vor der Intervention wird ein vorzugsweise tomographisches 3-D-Bild eines Zielbereiches der Intervention aufgezeichnet,
• – während der Intervention wird ein 2-D-Bild des Zielbereiches aufgezeichnet und mit dem 3-D-Bild registriert, werden/wird:
• – im 2-D-Bild sichtbare Bildmerkmale von sich bewegenden Strukturen identifiziert bzw. automatisch ermittelt,
• – in weiteren, aus der gleichen Projektion aufgenommenen 2-D-Bildern aus diesen sichtbaren Bildmerkmalen die Bewegung des Patienten bestimmt,
• – weitere, im 2-D-Bild vorhandene Bildmerkmale als sogenannte anatomische Fixpunkte von starren und/oder nahezu starren und/oder von der Bewegung unabhängigen Strukturen identifiziert bzw. ermittelt,
• – ausgehend von den genannten Fixpunkten für jeden weiteren Bildpunkt eine Korrektur der 2-D/3-D-Registrierung zum Ausgleich der zuvor bestimmten Bewegung berechnet und
• – die 2-D-Bilder überlagert mit dem 3-D-Bild visualisiert werden.

The invention relates to a method for movement correction during imaging during a medical intervention of a patient. Starting from the steps:

• Before the intervention, a preferably tomographic 3-D image of a target area of the intervention is recorded,
• - during the intervention, a 2-D image of the target area is recorded and registered with the 3-D image, will / will:
• Identifies image features of moving structures that are visible in the 2-D image, or determines them automatically,
• In further, from the same projection recorded 2-D images from these visible image characteristics determines the movement of the patient,
• Further image features present in the 2-D image are identified or determined as so-called anatomical fixed points of rigid and / or nearly rigid and / or movement-independent structures,
• - calculated on the basis of said fixed points for each further pixel, a correction of the 2-D / 3-D registration to compensate for the previously determined movement and
• - The 2-D images are superimposed visualized with the 3-D image.

The invention further provides that the identified fixed points are connected to a fixed line with each other, preferably by a spline function, to mark an area independent of the movement in the 2-D image used in the correction of the 2-D / 3 D registration and the 3-D images and / or 2-D images ( 13 . 37 to 41 ) are adapted to the movement accordingly.

These Fixed line indicates areas that are not or only very slightly z. B. with breathing. By way of example, this could be the upper edge of the heart or those parts of the abdomen that are farther from the diaphragm lie.

In addition, can for the Fixed line at least one parameter can be introduced, which determines the degree of independence from the movement for defines the area mentioned.

One Another aspect of the invention is a device formed with modules for motion correction during imaging during a medical Intervention of a patient according to the above mentioned Process.

Of the Advantage of the invention is in particular that a movement correction in areas Being at an intervention very inhomogeneous with the breathing move (eg parts of the abdomen or the heart).

below is an embodiment of Invention described in more detail with reference to a drawing.

In show the drawing:

1 an X-ray diagnostic device for carrying out the method,

2 a view of the path of a detector and a radiation source around an object to be examined in the axial direction,

3 a schematic view of the registration of a 3-D reconstruction of the vascular system of the liver and a 2-D fluoroscopic image of a catheter in the liver,

4 a schematic representation of the ribcage to illustrate the respiratory movements,

5 a 2-D fluoroscopic image with superimposed 3-D volume (outlines) according to the procedure of the earlier patent application DE 10 2007 015 792.6 .

6 a schematic representation of the procedure according to the invention for movement correction

7 a schematic representation of the result of the movement correction according to the invention

From the US 2006/0120507 A1 is an X-ray diagnostic device known, for example, in the 1 is shown, the one on a stand 1 rotatably mounted C-arm 2 has at its ends an X-ray source, for example an X-ray source 3 , and an X-ray image detector 4 are attached.

The X-ray image detector 4 may be a rectangular or square semiconductor flat detector, preferably made of amorphous silicon (aSi).

In the beam path of the X-ray source 3 there is a patient table 5 for example, to receive a heart of a patient to be examined. At the X-ray diagnostic device is an image system 6 connected that the image signals of the X-ray image detector 4 receives and processes.

For the creation of 3-D data records, the rotatably mounted C-arm 2 with X-ray source 3 and X-ray image detector 4 turned so that, like the 2 schematically in plan view of the axis of rotation shows itself in an orbit 7 the X-ray source 3 as well as an orbit 8th the X-ray image detector 4 around an object to be examined 9 move. The orbits 7 and 8th can be completely or partially traversed to create a 3-D data set.

In the object to be examined 9 it may be, for example, an animal or human body but also a phantom body.

The X-ray source 3 emits one of a beam focus of the X-ray source 3 outgoing beam 10 pointing to the x-ray image detector 4 meets.

The X-ray source 2 and the X-ray image detector 4 each run around the object 5 around that, the X-ray source 2 and the X-ray image detector 4 on opposite sides of the object 5 are opposite.

Based on 3 The registration according to the prior art will now be briefly explained. A 3-D image 11 shows a 3-D reconstruction of the vascular system 12 a liver. In a 2-D fluoroscopic image 13 is a catheter 14 presented in the liver. An arrow 15 indicates a registration and overlay of both images 11 and 13 to a sub-picture 16 for the purpose of navigation, in which the catheter 14 is visible. Because the 2-D fluoroscopic image 13 Respiratory movements, the 3-D image 11 However, depending on the respiratory phase, the impression is that the catheter is rigid 14 outside the vascular system 12 in the direction of the double arrow 17 moved periodically.

For this reason, the older patent application goes DE 10 2005 059 804 A1 the way that every new 2-D fluoroscopic image 13 again with the 3-D image 11 is registered.

The 4 shows a schematic representation of the assumptions about the respiratory correction. In the ribcage 18 squeeze the lungs 19 breathing the diaphragm 20 down, that's the movement to the abdomen 21 passes. The by the double arrow 22 characterized respiratory movement and thereby induced by double arrows 23 marked, to the abdomen 21 The respiratory movement that is passed on thus has a clear preferred direction, especially for all X-ray projections along the "diaphragmatic plane", the usual image plane in abdominal interventions. The actual movement visible in the x-ray projection is, of course, much more complex and generally also contains a component of rotation or distortion. Simplified, however, it can be understood as translation in the image plane with a certain preferred direction.

5 shows a 2D fluoroscopic image with a registered superimposed 3-D volume 25 , wherein the outlines are indicated by the volume. In the 5 becomes an anatomical finding of the respiratory movement, as already in DE 10 2007 015 792.6 has been proposed schematically indicated. In a fluoroscopy series with a registered and superimposed 3-D volume certain features or structures such. B. ribs 24 , a catheter 26 and line features, tracked from one image to the next. These can either be determined by the user (eg by marking the structures, eg the catheter 26 etc.), or automatically (also on a marked portion of the image) are found and tracked (eg, with methods of so-called optical flow). Together with a possibly known preferred direction 29 is then from these individual shifts z. B. 27 a plausible overall direction of movement 28 calculated (ie a correction from one image to the next). With this correction, the 3-D overlay is now shifted to match each correction direction calculated for an image.

In 6 the procedure according to the invention for movement correction is schematically indicated. In addition to that too 5 described, the user will now see some anatomical "on fixed points" 30 marked points that typically denote little or no respiratory motion. In the heart of this z. B. be the upper heart areas. These fixpoints can be connected by the system to a "fix line", eg. B. by a so-called spline function.

As in 7 With 33 indicated, the 3-D overlay is not static shifted but rather "warped", in which for each point of the overlay an individual correction direction 31 is calculated. This corresponds z. B. far from the fixed point line of the full correction direction 32 while near the fixed point line it corresponds to almost no or no correction. In the areas in between, the correction is interpolated accordingly.

An assumption made for the method according to the invention consists in the fact that the respiratory movement takes place in the image plane and is possibly further subject to a certain preferred direction. For physiological reasons, this runs along the body axis, for example. In the from the usual projection directions (especially the AP projections recorded 3-D images corresponds to a movement in "up-dressing").

• 1. Wie in der älteren Patentanmeldung DE 10 2007 015 792.6 schon vorgeschlagen, wird anhand der Bildinformation eine Atemkorrekturrichtung berechnet. Dies kann z. B. durch Verfolgen von Strukturen im Fluoroskopiebild geschehen, die sich synchron zu der Atmung bewegen, beispielsweise a) einen Teil des Katheters oder Führungsdrahtes etc. und/oder b) eine entsprechende anatomische Region und/oder c) ein zu diesem Zwecke ein- oder aufgebrachten speziellen Marker oder ähnliches. Diese Strukturen können vom Benutzer aus seiner physiologischen Erfahrung heraus markiert werden. Diese Strukturen können jedoch auch automatisch gefunden werden (auch auf einem markierten Teilbereich des Bildes). Eine entsprechende Verschiebung (evtl. zusammen mit einer bekannten Vorzugsrichtung) wird als Atembewegung interpretiert (siehe 5).
• 2. Zusätzlich werden im Bild vom Benutzer gewisse anatomische „Fixpunkte” markiert (siehe 6 und 7), die Punkte mit typischerweise wenig oder gar keiner Atembewegung bezeichnen. Im Herzen können dies z. B. die oberen Herzbereiche sein.
• 3. Diese Fixpunkte können vom System zu einer „Fixlinie” verbunden werden, z. B. durch eine sogenannte Spline-Funktion. Dies kennzeichnet dann einen atemstabilen Bereich.
• 4. Zusätzlich kann für diese Fixlinie noch ein Parameter, beispielsweise aus dem Intervall zwischen 0 und 1, angegeben werden. Dieser bezeichnet, wie starr die Fixpunkte oder -linie sein soll. Null bedeutet beispielsweise, dass sich die Punkte überhaupt nicht mit der Atmung bewegen. Eins kann bedeuten, dass sich die Punkte so verhalten wie die im Bild ermittelte Atembewegung. Dies wäre dann der Spezialfall der „starren” Verschiebung wie sie beispielsweise in 5 gezeigt wird. Das 3-D-Overlay wird „gewarpt” (z. B. verformt, gestreckt, gestaucht bzw. gedreht), in dem für jeden Punkt des Overlay eine individuelle Korrekturrichtung berechnet wird. Diese entspricht beispielsweise weit entfernt von der Fixpunktlinie der vollen unter 1. berechneten Korrekturrichtung, während sie nahe der Fixpunktlinie nahezu keiner Korrektur entspricht. In den Bereichen dazwischen wird die Korrektur entsprechend interpoliert. Dieses Vorgehen zur Korrektur liefert ein sich den unterschiedlichen Bewegungen optimal angepasstes Ergebnis. Es können vor allem Korrekturen für Bereiche vorgenommen werden, die sich inhomogen mit der Atmung verschieben (z. B. im Herzen).

Also for physiological reasons, the breathing movement in the 2D image has certain "fixed points", ie areas that do not or only very slightly with the breathing. Examples include the upper edge of the heart and the parts of the abdomen that are farther from the diaphragm. Starting from a 3-D volume data set registered to the 2-dimensional fluoroscopic image (2D image) (either native or as 3-D angiography), the respiratory correction preferably proceeds as follows:

• 1. As in the earlier patent application DE 10 2007 015 792.6 already proposed, a respiratory correction direction is calculated on the basis of the image information. This can be z. Example, by tracking structures in Fluoroskopiebild happen that move synchronously to the breathing, for example, a) a part of the catheter or guide wire, etc. and / or b) a corresponding anatomical region and / or c) a for this purpose on or applied special marker or the like. These structures can be tagged by the user out of his physiological experience. However, these structures can also be found automatically (even on a marked part of the image). A corresponding shift (possibly together with a known preferred direction) is interpreted as respiratory movement (see 5 ).
• 2. In addition, certain anatomical "fixed points" are marked in the image by the user (see 6 and 7 ), which designate points with typically little or no respiratory motion. In the heart of this z. B. be the upper heart areas.
• 3. These fixed points can be connected by the system to a "fixed line", eg. B. by a so-called spline function. This then marks a breath-stable area.
• 4. In addition, a parameter, for example from the interval between 0 and 1, can be specified for this fix line. This indicates how rigid the fixed points or lines should be. Zero means, for example, that the points do not move at all with the breathing. One thing can mean that the points behave in the same way as the breathing movement determined in the picture. This would then be the special case of the "rigid" shift as in, for example, 5 will be shown. The 3-D overlay is "warped" (eg, deformed, stretched, compressed, or rotated) by calculating an individual correction direction for each point of the overlay. For example, this corresponds far from the fixed point line of the full correction direction calculated under 1., while it corresponds to almost no correction near the fixed point line. In the areas in between, the correction is interpolated accordingly. This procedure for correction provides a result optimally adapted to the different movements. In particular, corrections can be made for areas that are inhomogeneous with respiration (eg, in the heart).

In the context of the invention, the tomographic imaging device may be, for example, X-ray C-arm systems, X-ray biplane devices, computer tomographs, MR or PET. Instead of in 1 illustrated stand 1 Floor and / or ceiling stands can also be used. The C-arm 2 can also by a so-called electronic C-arm 2 be replaced, in which an electronic coupling of X-ray source 3 and X-ray image detector 4 he follows. The C-bows 2 but can also be guided on robot arms, which are attached to the ceiling or floor. Also, the method can be performed with X-ray machines, in which the individual image-forming components 3 and 4 are each held by a robot arm, which are arranged on the ceiling and / or floor.

literature

• [1] Graeme Patrick Penney, Registration of Tomographic Images to X-ray Projections for Use in Image Guided Interventions PhD thesis, University College London, CISG, Division of Radiological Sciences, Guy's Hospital, King's College London, London SE1 9RT England, 2000, pages 97 to 160
• [2] Chris Harris and Mike J. Stephens, A combined corner and edge detector, In Alvey Vision Conference, pages 147-151, 1988.

1

stand

2

C-arm

3

X-ray source

4

X-ray image detector

5

Patient table

6

image system

7

orbit

8th

orbit

9

object

10

ray beam

11

3-D image

12

vascular system

13

2-D fluoroscopic image

14

catheter

15

arrow

16

Overlay image

17

arrow

18

thorax

19

lung

20

diaphragm

21

abdomen

22

double arrow (Diaphragm movement while breathing)

23

double arrows (respiratory movement transmitted to the abdomen)

24

ribs and line characteristics

25

To the Fluoroscopy image registered and superimposed 3D volume (outlines)

26

catheter and line characteristics

27

double arrows (Direction of movement of the individual features)

28

double arrows (overall direction of movement calculated from the preferred direction and individual directions of movement)

29

Preferred direction such. B. 22 and 23

30

fixed points (possibly connected to a fixed line)

31

individual Correction to each pixel

32

suitor Area (full correction)

33

"Scarred" respiratory correction (Schematically)

Claims (6)

Method for motion correction in imaging during a medical intervention of a patient, in which: - before the intervention, a preferably tomographic 3-D image ( 11 ) of a target area of the intervention is recorded, - during the intervention, a 2-D image ( 13 ) of the target area and with the 3-D image ( 11 . 25 ) is registered, - in the 2-D image ( 13 ) visible image features ( 24 . 26 ) of moving structures ( 14 . 24 . 26 ) are detected automatically, - in further 2-D images recorded from the same projection ( 13 ) from these visible image features ( 24 . 26 ) the movement ( 28 ) of the patient, - further, in the 2-D image ( 13 ) existing image features as so-called anatomical fixed points ( 30 ) are determined by rigid and / or nearly rigid and / or motion-independent structures, - starting from the above-mentioned fixed points ( 30 ) for each further pixel a correction ( 31 . 32 ) of the 2-D / 3-D registration to compensate for the previously determined movement ( 28 ) and - the 2-D images ( 13 ) overlaid with the 3-D image ( 11 . 25 ), characterized in that the determined fixed points ( 30 ) may be connected to a fixed line with each other preferably by a spline function to designate an area independent of the movement in the 2-D picture which is used in the correction ( 31 . 32 ) of the 2-D / 3-D registration, and that the 3-D images ( 11 . 25 ) and / or 2-D images ( 13 ) the movement ( 28 ) are adjusted accordingly. Method according to claim 1, characterized in that the image characteristics (resp. 24 . 26 ) are determined so that a compensation of the respiratory movement of the patient takes place. Method according to one of the preceding claims, characterized in that the registration based on the previously determined movement ( 28 ) is corrected in real time. Method according to one of the preceding claims, characterized characterized in that from the structures complex movements, in particular rotation and / or distortion. Method according to one of the preceding claims, characterized marked that for the fixed line at least one parameter is introduced, which determines the degree of independence from the movement for the specified area. Device designed with modules for motion correction during imaging during a medical intervention of a patient according to the method according to one of the preceding claims.